Cold temperature stable biocidal composition

ABSTRACT

Provided is a synergistic biocidal composition comprising a biocidal N-(2-nitroalkyl) morpholine compound of formula I: 
     
       
         
         
             
             
         
       
     
     where R, x, and y are as defined herein, together with an aromatic alcohol. The composition is cold temperature stable and is therefore useful for the control of microorganisms in a variety of matrices, including liquid fuels.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims benefit of priority from U.S. Provisional Patent Application No. 61/166,934, filed Apr. 6, 2009, which application is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The invention relates to cold temperature stable and synergistic biocidal compositions suitable for use in various aqueous and non aqueous matrices, such as liquid fuels.

BACKGROUND OF THE INVENTION

N-(2-nitroalkyl) morpholine compounds are a class of biocides that are useful for controlling microorganism growth in a variety of environments, such as industrial cooling water systems, recycle process water systems, oil and gas recovery operations, and in fuels. FUELSAVER™, which is based on a mixture of N-(2-nitrobutyl)morpholine and 2-ethyl-2-nitro-1,3-dimorpholinopropane, is an example of a commercially available N-(2-nitroalkyl) morpholine biocide that is used for preserving fuels.

While N-(2-nitroalkyl) morpholines are effective biocides, many crystallize at temperatures above 0° C. Such biocides, therefore, are generally unsuitable for cold temperature applications, storage, or transport.

It would be an advance in the art to provide formulations of N-(2-nitroalkyl) morpholines that are cold stable, particularly those that are stable (i.e., do not freeze) at temperatures as low as −20° C. It would also be an advance to provide formulations that exhibit enhanced activity against a broad spectrum of microorganisms.

BRIEF SUMMARY OF THE INVENTION

In one aspect, the invention provides a biocidal composition that is stable at low temperature and exhibits synergistic behavior. The composition comprises an N-(2-nitroalkyl) morpholine compound of formula I:

where R, x, and y are as defined herein, together with an aromatic alcohol.

In another aspect, the invention provides a fuel blend. The fuel blend comprises a liquid fuel and the cold temperature stable biocidal composition described herein.

In a further aspect, the invention provides a method for imparting microorganism resistance to a matrix in need of such resistance. The method comprises including in the matrix an effective amount of the biocidal composition described herein.

DETAILED DESCRIPTION OF THE INVENTION

As noted above, the invention provides cold temperature stable biocidal compositions. In particular, compositions according to the invention have been found to be freeze stable (i.e., do not freeze) to temperatures as low as −20° C. This occurs even though the individual components of the composition are not themselves freeze stable at the same temperatures.

In addition to cold temperature stability, compositions according to the invention also exhibit improved control of microorganism growth when compared to other non-inventive cold temperature stable formulations.

For the purposes of this specification, the meaning of “microorganism” includes, but is not limited to, bacteria, fungi, algae, and viruses. The words “control” and “controlling” should be broadly construed to include within their meaning, and without being limited thereto, inhibiting the growth or propagation of microorganisms, killing microorganisms, disinfection, and/or preservation against re-growth of microorganisms.

The composition of the invention comprises: a biocidal N-(2-nitroalkyl) morpholine compound of the formula I:

where R is hydrogen, methyl or ethyl; x is 1 or 2; y is 0 or 1, and the sum of x and y is 2; and an aromatic alcohol.

Preferred biocidal compounds of formula I are those in which R is ethyl.

Also preferred are compounds in which y is 1.

Additionally preferred are compounds wherein y is 0.

Specific examples of preferred compounds of formula I include: N-(2-nitroethyl)morpholine, N-(2-nitropropyl)morpholine, N-(2-nitrobutyl)morpholine, 2-nitro-1,3-dimorpholinopropane, 2-methyl-2-nitro-1,3-dimorpholinopropane, 2-ethyl-2-nitro-1,3-dimorpholinopropane, or mixtures of two or more thereof.

More preferred are N-(2-nitrobutyl)morpholine and 2-ethyl-2-nitro-1,3-dimorpholinopropane.

Particularly preferred is a mixture of N-(2-nitrobutyl)morpholine and 2-ethyl-2-nitro-1,3-dimorpholinopropane. In this embodiment, it is further preferred that the weight ratio of N-(2-nitrobutyl)morpholine to 2-ethyl-2-nitro-1,3-dimorpholinopropane is between about 20:1 and about 10:1, more preferably between about 18:1 and about 14:1.

The aromatic alcohol used in the compositions of the invention functions as a freeze stabilizer and also as an enhancer of biocidal efficacy. Suitable aromatic alcohols include phenoxyethanol, benzyl alcohol, and aromatic glycol ethers. Preferred is phenoxyethanol.

The composition of the invention preferably comprises between about 5 and 95 weight percent, more preferably between about 15 and 75 weight percent, even more preferably between about 30 and 55 weight percent, and further preferably between about 38 and 44 weight percent of the N-(2-nitroalkyl) morpholine compound based on the total weight of the biocide and the aromatic alcohol in the composition.

An especially preferred composition according to the invention comprises from about 38 to 44 weight percent of a mixture of N-(2-nitrobutyl)morpholine and 2-ethyl-2-nitro-1,3-dimorpholinopropane and about 62 to 56 weight percent of phenoxyethanol, based on the total weight of the mixture of N-(2-nitrobutyl)morpholine/2-ethyl-2-nitro-1,3-dimorpholinopropane and the phenoxyethanol present in the composition.

The composition may contain other additives including, but not limited to, other aromatic or non-aromatic solvents, glycolic type solvents, and non-aromatic glycol ethers, as well as various inert or byproduct material that may result from the synthesis of the biocide and that are not removed during workup. In general, it is preferred that the total amount of biocide compound and aromatic alcohol comprise at least about 70 weight percent, more preferably at least about 80 weight percent of the composition, based on the compositions total weight.

As noted, more than one N-(2-nitroalkyl) morpholine compound can be combined for use in the invention; in such cases, ratios and concentrations are calculated using the total weight of all N-(2-nitroalkyl) morpholine compounds present.

N-(2-nitroalkyl) morpholine compounds for use in the invention are commercially available or can be readily prepared by those skilled in the art using well known techniques (see e.g., U.S. Pat. No. 3,054,749 and Canadian patent 982475, both incorporated by reference). Aromatic alcohols are also commercially available or can be readily prepared.

The compositions of the invention are useful at controlling microorganism growth in a variety of aqueous and non-aqueous matrices and in matrices that are mixtures of aqueous and non-aqueous components. Examples include, but are not limited to, metalworking fluids, die cast lubricants, mold release agents, paints, paint spray booth wash water, coatings, adhesives, caulks, sealants, mineral slurries, inks, petroleum (crude oil), or liquid fuels such as gasoline, diesel, biodiesel, water-fuel emulsions, ethanol-based fuels, ether-based fuels, diesel oil, fuel oil, or kerosene based fuels. Because of their cold temperature stability, the compositions of the invention are particularly suitable for controlling microorganisms in liquid fuels.

A person of ordinary skill in the art can readily determine, without undue experimentation, the effective amount of the composition that should be used in any particular matrix to provide microorganisms control. By way of illustration, a suitable effective amount (total for the N-(2-nitroalkyl) morpholine compound(s) and the aromatic alcohol) is at least about 25 ppm or at least about 500 ppm, by weight. Typically, the amount is less than about 20,000 ppm or less than about 2500 ppm, by weight.

The components of the composition of the invention can be added to the matrix separately or they can be preblended prior to addition. A person of ordinary skill in the art can readily determine the appropriate method of addition. Preblending is preferred.

The following examples are illustrative of the invention but are not intended to limit its scope. Unless otherwise indicated, ratios, percentages, parts, and the like used herein are by weight.

EXAMPLES

In the Examples below, the following compositions are tested:

-   Sample A: a comparative composition that contains an 86 weight     percent mixture of N-(2-nitrobutyl)morpholine and     2-ethyl-2-nitro-1,3-dimorpholinopropane as the biocidal actives     (NBM/ENDM). The ratio of NMB/ENDM is 16.2:1. The balance of the     composition are inerts/byproducts created during the synthesis of     the biocidal actives. The composition does not contain     phenoxyethanol. Available from The Dow Chemical Company as     FUELSAVER™ Antimicrobial. -   Sample B: an inventive composition that contains about 55 weight     percent of phenoxyethanol and about 45 weight percent of Sample A.

Sample C: a comparative composition that is freeze stable and that contains a mixture of about 55 weight percent tripropylene glycol methyl ether as a freeze stabilizer and about 45 weight percent of Sample A. The composition does not contain phenoxyethanol.

-   Phenoxyethanol (PHE): an aromatic alcohol obtained from The Dow     Chemical Company as DOWANOL™ EPh. -   Tripropylene Glycol Methyl Ether (TPM): a non-aromatic alcohol that     can be used as a freeze stabilizer. It is available from The Dow     Chemical Company as DOWANOL™ TPM.

Example 1 Freeze-Thaw Stability Testing

Sample A (comparative composition), Sample B (inventive), and phenoxyethanol (comparative) are placed in a −20° C. freezer for 24 hours, removed and observed for freezing. Samples are thawed completely and then replaced in the freezer for another 24 hour period. This procedure is carried out for five cycles in which the samples are placed in the freezer for five 24 hour periods. Sample size is 5 ml in a clear glass container with a Bakelite screw top. Results are summarized in Table 1.

TABLE 1 Freeze Thaw Study: 5 Cycle in −20° C. Freezer In: Out: Thawed In- Out: Thawed In- Out: Thawed In: Out: Thawed In- Out: Thawed Sample Day 1 3 hours Day 2 3 hours Day 3 3 hours Day 4 3 hours Day 5 3 hours Sample B Not Not Not Not Not Not Not Not Not Not (inventive) frozen frozen frozen frozen frozen frozen frozen frozen frozen frozen Sample A Frozen Thawed Frozen Thawed Frozen Thawed Frozen Thawed Frozen Thawed (comparative) Phenoxyethanol Frozen Thawed Frozen Thawed Frozen Thawed Frozen Thawed Frozen Thawed (comparative)

As can be seen from the data in Table 1, the inventive composition (Sample B) does not freeze even though the individual ingredients, the biocide mixture (Sample A) and the phenoxyethanol, both freeze under the same temperature conditions.

Example 2 Microbial Control Experiments

This example compares the efficacy of compositions of the invention to non-inventive compositions, in diesel fuel, against various microorganisms.

Procedure

Bacteria: Pseudomonas aeruginosa (ATCC# 33988), Yeast: Yarrowia tropicalis (ATCC# 48138), and Mold: Hormoconis resinae ATCC# 20495, are sub-cultured in Bushnell-Haas broth, and used for the inoculum of this example. Bushnell-Haas broth is used as the aqueous phase below the diesel fuel. Testing is carried out for 4 weeks. Microbial survival is measured using the plate count method. Tryptic soy agar is used for Pseudomonas aeruginosa, and Sabouraud dextrose agar with 0.5 ug/ml gentamycin for Yarrowia tropicalis, and bacteriological grade agar 1.5%, with 0.01% potassium tellurite for Hormoconis resinae. Bacteria are incubated at 37° C. for 48 hours, and fungi at 25° C. for 5-7 days.

Testing is carried out in glass bottles with bakelite screw tops. Volumes: 130 ml diesel fuel over 25 ml synthetic water bottom (Bushnell-Haas Broth). Tests are mixed weekly by turning the bottle upside down 5 times.

The diesel fuel is obtained from Halternann Products (Channelview, Tex.) Diesel fuel, with the following specifications: 2007 Certification Diesel, GMPT-5-0,9-; Product Number: HF 582b; Product Code: 20582b.

Table 2 shows results for “Sample B”, a composition according to the invention. Table 3 shows results for “Sample C,” a comparative composition that is freeze stable. Table 4 shows results for phenoxyethanol which is a component in Sample B, but is not freeze stable by itself. Table 5 is a summary of the lowest dosage required to reduce the concentration of viable microorganisms to a <10 CFU/mL level for Samples B, C, and phenoxyethanol.

TABLE 2 Biocidal Efficacy: Inventive Composition Sample B Day Bacteria Yeast Mold Control (no biocide) 30 4.3E8 8.3E7 6.7E6  500 ppm 30 8.0E2 5.6E2 2.6E3  750 ppm 30 2.8E2 1.8E2 7.0E2 1000 ppm 30 <10 <10 3.8E2 1500 ppm 30 <10 <10 <10 2000 ppm 30 <10 <10 <10 2500 ppm 30 <10 <10 <10 Day 0: Bacteria 8.7E7 cfu/ml; Yeast 2.3E7 cfu/ml; Mold 4.6E6 cfu/ml

TABLE 3 Biocidal Efficacy: Comparative Composition Sample C Day Bacteria Yeast Mold Control (no biocide) 30 4.3E8 8.3E7 6.7E6  500 ppm 30 9.0E3 1.3E4 6.8E4  750 ppm 30 7.8E3 5.6E3 1.1E4 1000 ppm 30 1.1E3 8.4E2 8.0E3 1500 ppm 30 4.0E2 2.8E2 3.9E3 2000 ppm 30 <10 6.0E1 7.0E2 2500 ppm 30 <10 <10 <10 Day 0: Bacteria 8.7E7 cfu/ml; Yeast 2.3E7 cfu/ml; Mold 4.6E6 cfu/ml

TABLE 4 Biocidal Efficacy: Phenoxyethanol Day Bacteria Yeast Mold Control (not biocide) 30 4.3E8 8.3E7 6.7E6  500 ppm 30 4.7E6 2.0E6 7.3E5  750 ppm 30 1.3E6 7.2E5 6.7E5 1000 ppm 30 4.8E5 1.8E5 5.6E5 1500 ppm 30 6.0E4 7.3E4 9.0E4 2000 ppm 30 1.7E4 5.5E4 7.8E4 2500 ppm 30 9.6E3 2.3E4 5.5E4 Day 0: Bacteria 8.7E7 cfu/ml; Yeast 2.3E7 cfu/ml; Mold 4.6E6 cfu/ml

TABLE 5 Lowest dosage required to reduce the concentration of viable microorganism to <10 CFU/mL level (ppm). ppm of ppm of ppm of NMB/ENDM NMB/ENDM PHE in in ppm in Sample B Sample B Sample C PHE Bacteria 387 550 774 >2500 Yeast 387 550 968 >2500 Mold 581 825 968 >2500

As can be seen from the data, the inventive composition (Sample B) provides significantly improved microbial control relative to the other low temperature stable formulation (Sample C), as well as relative to phenoxyethanol which is not freeze stable nor very effective as a microbial control agent.

Example 3 Synergy of Inventive Compositions

Sample A and Sample C were re-tested at the same biocidal active concentrations using the test method described in Example 2, except the test was carried out for 7 days and the microbial survival was measured at 24 hour and at 7 days. The results are summarized in Table 6.

TABLE 6 Comparison of the efficacy of Sample A and Sample C at equivalent NMB/ENDM active concentrations Microbial growth after biocide treatments at 24 h and 7 days NMB/ENDM Bacteria Yeast Contact Concentration Sample Sample Sample Sample time (ppm) A C A C 24 hours 0 (Control) 2.0E7 2.0E7 1.2E5 1.2E5 194 6.0E4 <10 1.1E4 2.7E3 387 <10 <10 <10 <10 774 <10 <10 <10 <10  7 days 0 (Control) 1.1E9 1.1E9 4.0E5 4.0E5 194 <10 <10 <10 <10 387 <10 <10 <10 <10 774 <10 <10 <10 <10 Day 0: Bacteria 4.0E6 cfu/ml; Yeast 6.1E6 cfu/ml; Mold 4.0E7 cfu/ml

As shown in Table 6, at equivalent active concentrations, Sample A had generally lower efficacy than Sample C.

Because Sample A is generally less effective than Sample C at the same active concentrations, the data results from Table 5 are used to determine the concentrations of NMB/ENDM in Sample C that are required to achieve a <10 CFU/mL level, to estimate the synergy index between NMB/ENDM and phenoxyethanol. Based on the Synergy Index (SI) calculation equation below, the estimated synergy indices for NMB/ENDM and phenoxyethanol are provided in Table 7.

Synergy Index=Ca/CA+Cb/CB

Ca: Concentration of NMB/ENDM in Sample B required to reduce the concentration of viable microorganism to <10 CFU/ml level

CA: Concentration of NMB/ENDM required to reduce the concentration of viable microorganism to <10 CFU/ml level when used alone

Cb: Concentration of PHE in Sample B required to reduce the concentration of viable microorganism to <10 CFU/ml level

CB: Concentration of PHE required to reduce the concentration of viable microorganism to <10 CFU/ml level when used alone

-   -   <1: synergy

Synergy Index=1: additivity

-   -   >1: antagonism

TABLE 7 Estimated synergy indices between NMB/ENDM and phenoxyethanol ppm of ppm of ppm of NMB/ENDM in PHE in NMB/ Sample B Sample B ENDM PHE Synergy (Ca) (Cb) (CA) (CB) Index Bacteria 387 550 >774 >2500 <0.72 Yeast 387 550 >968 >2500 <0.62 Mold 581 825 >968 >2500 <0.93

The results in Table 7 illustrate that there is a synergistic effect between NMB/ENDM and phenoxyethanol.

While the invention has been described above according to its preferred embodiments, it can be modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using the general principles disclosed herein. Further, the application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the following claims. 

1. A cold temperature stable biocidal composition comprising: a compound of the formula I:

where R is hydrogen, methyl or ethyl; x is 1 or 2; y is 0 or 1, and the sum of x and y is 2; and an aromatic alcohol.
 2. The cold temperature stable biocidal composition of claim 1, wherein R is ethyl.
 3. The cold temperature stable biocidal composition of claim 1, wherein y is
 1. 4. The cold temperature stable biocidal composition of claim 1, wherein y is
 0. 5. The cold temperature stable biocidal composition of claim 1, wherein the compound of formula (I) is selected from: N-(2-nitroethyl)morpholine, N-(2-nitropropyl)morpholine, N-(2-nitrobutyl)morpholine, 2-nitro-1,3-dimorpholinopropane, 2-methyl-2-nitro-1,3-dimorpholinopropane, 2-ethyl-2-nitro-1,3-dimorpholinopropane, and mixtures of two or more thereof.
 6. The cold temperature stable biocidal composition of claim 1, wherein the compound of formula (I) comprises a mixture of N-(2-nitrobutyl)morpholine and 2-ethyl-2-nitro-1,3-dimorpholinopropane.
 7. The cold temperature stable biocidal composition of claim 1, wherein the aromatic alcohol is selected from phenoxyethanol, benzyl alcohol, and aromatic glycol ethers.
 8. The cold temperature stable biocidal composition of claim 1, wherein the compound of formula (I) comprises a mixture of N-(2-nitrobutyl)morpholine and 2-ethyl-2-nitro-1,3-dimorpholinopropane and the aromatic alcohol is phenoxyethanol.
 9. A blend comprising a liquid fuel and the biocidal composition of claim
 1. 10. A blend according to claim 9 wherein the liquid fuel is gasoline, diesel, biodiesel, a water-fuel emulsion, an ethanol-based fuel, an ether-based fuel, diesel oil, fuel oil, or kerosene based fuel.
 11. A method for providing microorganism resistance to a matrix susceptible to growth of microorganisms, the method comprising including in the matrix an effective amount of the biocidal composition of claim
 1. 12. The method of claim 11 wherein the matrix is aqueous, non-aqueous, or a mixture of aqueous and non-aqueous.
 13. The method of claim 12 wherein the matrix is a metalworking fluid, a die cast lubricant, a mold release agent, a paint, paint spray booth wash water, a coating, an adhesive, a caulk, a sealant, a mineral slurry, an ink, petroleum (crude oil), or a liquid fuel.
 14. The method of claim 13 wherein the liquid fuel is gasoline, diesel, biodiesel, a water-fuel emulsion, an ethanol-based fuel, an ether-based fuel, diesel oil, fuel oil, or kerosene based fuel. 